/Engine/Source/Runtime/Engine/Classes/PhysicsEngine/PhysicsConstraintComponent.h
Pass in reference position in (maintains reference orientation). If the constraint is currently active, this will set its active local pose. Otherwise the change will take affect in InitConstraint.
void SetConstraintReferencePosition ( [EConstraintFrame::Type](API\Runtime\PhysicsCore\Chaos\EConstraintFrame__Type) Frame, const FVector & RefPosition )